When I turn on the hot water, it only comes out for about 30 seconds, but then gets really cold and stays cold if I leave the water on (I've only tested for about 20 minutes, but it stays cold for those 20 minutes). However, if I turn the water off after the 30 seconds it's hot and as soon as the water gets cold, wait 1-2 minutes then turn the hot water back on, it's hot again for about 30 seconds before it gets goes cold again. Anyone have an idea of what the problem is?